The drilling of wells utilizing high-intensity laser light was proposed in the seventies as an alternative to the drilling with mechanical drills, as per the references cited below in the present specification.
In this respect, U.S. Pat. No. 3,977,478 to Shuck states that laser drilling of subterranean earth formations is efficiently accomplished by directing a collimated laser beam into a bore hole in registry with the earth formation and transversely directing the laser beam into the earth formation with a suitable reflector. The bore hole is highly pressurized with a gas so that as the laser beam penetrates the earth formation the high pressure gas forces the fluids resulting from the drilling operation into fissures and pores surrounding the laser-drilled bore so as to inhibit deleterious occlusion of the laser beam. Also, the laser beam may be dynamically programmed with some time dependent wave form, e.g., pulsed, to thermally shock the earth formation for forming or enlarging fluid-receiving fissures in the bore.
U.S. Pat. No. 3,988,281 to Salisbury and Stiles describes a method of earth boring, useful for oil well drilling and the like, employs a high powered laser beam focused and directed by appropriate optics and/or scanning means to a vertically downwardly directed annular pattern. A fluid blast means directed generally into the bore hole is disposed adjacent the beam between the earth and the optics or scanning means. The beam and fluid blast are alternately pulsed and the fluid blast is effective to create thermal shock in the core to shatter it and to deflect material cleared from the hole by the laser beam away from the boring apparatus.
U.S. Pat. No. 4,066,138, also to Salisbury and Stiles relates to an earth boring apparatus mounted above ground which directs an annulus of high powered laser energy downwardly for boring a cylindrical hole by fusing successive annular regions of the stratum to be penetrated at a power level that shatters and self-ejects successive cores from the hole. A first fluid blast above the hole deflects the ejected core as it exits from the hole. A second fluid blast above the hole ejects fluid to provide adequate fluid at the strata to be penetrated prior to actuation of the laser for promoting a thermal shock capable of shattering and ejecting the core. Optical sensing separately detects the core shattering and the core ejection to control timed actuation of the system components. The described array comprises a plurality of lasers symmetrically disposed around a common center.
In spite of all the advantages associated to the utilization of this drilling method not based on the physical contact between the drill bit and the surface to be drilled, among which, the drilling rate, absence of physical contact between the drill and the surface to be drilled, energetic efficiency, among others, the utilization of lasers in wells has not been commercially developed as a result of the absence of lasers bearing the minimal power required for efficient and competitive drilling as compared to mechanical devices.
Further drawbacks which have limited the practical implementation of the laser drilling of wells were the laser dimensions which rendered impossible their insertion in the drilled boreholes as well as the non existence of efficient (that is, of low confinement losses, high transparency and susceptibility control to the induction of non-linear phenomena) optical conveyors (optical fibers) which would enable the guidance of the laser light to long distances and locations of reduced dimensions and difficult access.
U.S. Pat. No. 4,090,572 to Welch and U.S. Pat. No. 4,113,036 to Stout are also directed to laser drilling.
U.S. Pat. No. 4,199,034 also to Salisbury and Stiles relates to a method of perforating the sub-surface formation located in the area of an oil or gas well bore hole comprising directing a high powered coherent light beam axially along the bore hole to a predetermined depth therein from a surface location, deflecting the beam at said depth along a deflected beam axis, and successively focusing the beam at said depth to concentrate the beam at each of a plurality of spaced focal points along the deflected beam axis. It is alleged that the method provides a significant increase in the distance (length) to which the calculated oil or gas bearing formations can be perforated and provides an accurate determination of the exact near horizontal plane orientation of such perforations so that each can be aimed in the direction of the most promising formation pay zone.
In the end of the nineties and beginning of the years 2000 compact, high powered laser systems become commercially available and the interest in their utilization for drilling wells is renewed. Besides the development of high powered lasers (based on different topologies and active materials, such as gas, dye, semiconductor, crystal, doped or not optical fiber, and others) the development of high-transparency, low confinement losses and non-linearity control optical fibers (mono mode, multi mode and having a diversity of cross section refraction index profiles and materials) is another motivating drive for the utilization of high-intensity laser light for drilling.
Upon utilization of optical fibers it is possible to convey high-intensity laser light to long distances—a few dozens of kilometers—while keeping the quality of the laser light (intensity and temporal and spatial coherences) at the output end of the fiber sufficiently high to secure the delivery of high optical densities, a condition which improves the efficiency of the drilling process.
More recently, the patent literature points out the following documents relevant to the subject.
U.S. Pat. No. 6,365,871 to Knowles et al. refers to a method of laser-drilling a hole through a workpiece, such as an injector nozzle (40), into a cavity comprising drilling a hole (41) through the workpiece (40) with a laser (50), providing a fluid having laser-barrier properties in the cavity so that, when the hole (41) is open to the cavity, laserlight passing through the hole (41) is incident upon the fluid whereby the workpiece (40) across the cavity from the hole (41) is protected from the laserlight, and arranging that the fluid does not enter the laser-drilled hole (41) during the drilling process. Apparatus for performing the method is also described.
U.S. Pat. No. 6,626,249 to Rosa relates to a geothermal drilling and recovery system comprising a drilling rig having an elevator with a laser and a radar gun mounted on said elevator, a drill pipe, a rotating mirror mounted adjacent the lower end of said drill pipe and means for establishing a vacuum adjacent said lower end of said drill pipe to remove and recover heat and drilling debris therefrom.
U.S. Pat. No. 6,755,262 to Parker relates to an earth boring apparatus at least partially locatable within a borehole. The apparatus includes a plurality of optical fibers, each of which has a proximal fiber light energy input end and a distal fiber light energy output end. At least one focal lens is disposed at the distal fiber light energy output end. The focal lens is made up of a plurality of focal elements, each of which corresponds to the distal fiber light energy output end of at least one optical fiber. The focal lens is arranged to receive light energy from the corresponding distal fiber light energy output end of the at least one optical fiber and focus it outwardly from the distal fiber light energy output end.
U.S. Pat. No. 6,870,128 to Kobayashi et al. provides to a method for boring a well with a laser beam, the method comprising: shining the laser beam into a conduit, wherein the laser beam is guided through the conduit by the internal reflectivity of said conduit; and extending the conduit into the well, so that the laser beam exiting the conduit shines onto an area in the well to be bored. A system for boring a well with a laser beam is also provided, the system comprising: a means for shining the laser beam into a conduit; wherein the laser beam is guided through the conduit by the internal reflectivity of said conduit; and a means for extending the conduit into the well, so that the laser beam exiting the conduit shines onto an area in the well to be bored. An apparatus is provided as well, comprising a conduit that is extendable into the well, and an inner surface inside of the conduit, wherein the inner surface is reflective to the laser beam.
U.S. Pat. No. 6,880,646 to Batarseh relates to a method and apparatus for providing fluid flow into a wellbore in which an apparatus having at least one laser energy output is lowered into the wellbore and the at least one laser energy output is directed at a wall of the wellbore. At least a portion of the wall is heated using the at least one laser energy output, whereby flow of a fluid into the wellbore is initiated and/or- enhanced.
U.S. Pat. No. 6,888,097 also to Batarseh describes an apparatus for perforation of wellbore walls, which apparatus includes a fiber optic cable having a laser input end and a laser output end. A laser source is operably connected to the laser input end and a laser head is connected to the laser output end. The laser head includes a laser control components for controlling at least one laser beam characteristic. Laser head control elements for controlling the motion and location of the laser head are operably connected to the fiber optic cable. The laser head is enclosed in a protective housing, which protects the fiber optic cable and elements, such as reflectors and lenses for controlling the laser beam emitted by the fiber optic cable disposed therein, from the harsh environments encountered in downhole operations.
In U.S. Pat. No. 7,416,258 to Reed apparatus and methods of using lasers are provided for spalling and drilling holes into rocks. A rock removal process is provided that utilizes a combination of laser-induced thermal stress and laser induced superheated steam explosions just below the surface of the laser/rock interaction to spall the rock into small fragments that can then be easily removed by a purging flow. Single laser beams of given irradiance spall rock and create holes having diameter and depth approximately equal to the beam spot size. A group of the single laser beams are steered in a controllable manner by an electro-optic laser beam switch to locations on the surface of the rock, creating multiple overlapping spalled holes thereby removing a layer of rock of a desired diameter. Drilling of a deep hole is achieved by spalling consecutive layers with an intermittent feed motion of the laser head perpendicular to the rock surface.
Published U.S. Application No 20080032152A1 to Vaughn et al. deals with the use of laser shock processing in oil and gas and/or petrochemical applications. The use includes subjecting friction stir weldments, fusion weldments, and other critical regions of ferrous and non-ferrous alloy components used in oil and gas and petrochemical applications to laser shock processing to create residual compressive stresses near the surface of the treated area. The residual compressive forces in the ferrous or non-ferrous components improve properties including, inter alia, surface strength, fatigue life, surface hardness, stress corrosion resistance, fatigue resistance, and environmental cracking resistance.
It should be pointed out that even for those patents providing the utilization of optical fiber(s) for deliver high-intensity laser light in bottom well locations no practical demonstrations of such possibility is provided when considered long fiber spans (deep wells, that is, >hundreds of meters). The main reason for this drawback is the induction of non-linear phenomena during high-intensity laser light propagation across long fiber spans. This is a classical problem in guided optics and several research groups and corporations have devoted efforts to reduce or eliminate it. In this respect see the reference by A. Mendes & T. F. Morse, “Specialty Optical Fibers Handbook”, Chapter 22, pp. 671-696, Elsevier, 2007
Among the various laser technologies, it should be pointed out the development of optical fiber laser where the high-intensity laser light is generated within the optical fiber itself. This laser is compact and generally does not require cooling even when operating at high intensities (≧kW). Further, the losses by coupling of the light at the laser output end with a conducting optical fiber (in charge of conveying the high-intensity laser light across long distances up to the region of interest) are minimal since it is a matter of fiber-fiber coupling and not free space-fiber.
As for the wavelength of the laser light, high-powered lasers of varied wavelengths (from ultraviolet to infrared) are available according to the active element and of the design of the laser cavity, as well as tunable wavelength lasers. This means that according to the nature of the surface to be drilled, it is possible to utilize a drilling wavelength which is coincident with the absorption band of the surface-constituent material. This increases significantly the efficiency of the process. Thus, during drilling it is possible to select in real time the most suitable laser wavelength for that particular surface. This is a further technological advantage of the laser drilling relative to conventional mechanical systems.
Besides the increase in drilling efficiency it is possible to utilize the information related to the optimum drilling parameters, such as wavelength(s), intensity and lasers operation regime for identifying the constituents of the drilled surface, that is, it is possible to assess the physical chemical, spectroscopic and mechanical log (porosity and resistance of the constituent of the drilled surface, and other properties) of the substrate drilled along the drilling axis in real time during drilling.
Soil logging is particularly important in the mining industry utilizing explosives for forming the gravel which will be later on processed to extract the mineral of interest. If the amount of explosives is excessive or less than the required load for forming optimum sized gravel, the processing is less efficient which means inferior utilization of the rock potential.